1. Field of the Invention
Aspects of the present invention relate to an image processing apparatus, and more particularly applied to a copier, an image scanning apparatus, or the like.
2. Description of the Related Art
When a document which is made by binding pieces of paper together (hereinafter such a document being referred to as a book-like document), such as a book or a booklet, is copied, a portion corresponding to the middle (a bound portion) of the book-like document when the book-like document is laid open tends to be darkened on a copy, hereinafter such a portion being referred to as a shadow region.
In the technology disclosed in Japanese Unexamined Patent Application Publication No. 9-284497, when a book-like document is copied, the occurrence of a shadow portion is avoided by specifying the shadow portion, converting the data obtained by scanning the specified portion into binary data according to a gray scale transform table, which is prepared in advance, and simply converting the data obtained by scanning the other portion into binary data without using the gray scale transform table.
However, the shadow region occurring when the book-like document is copied varies in area and in gray-scale level according to the thickness of the book-like document and what pages are to be copied. Thus, when a fixed gray scale transform table is used for such processing, the shadow region may be caused to be of a gray-scale level that is lighter than necessary, whereby a problem may occur in that, for example, text and the like near the shadow region disappear.
Moreover, when a thick book-like document is copied, a dark region (hereinafter, this region is also covered by the term “shadow region”) tends to occur at a portion corresponding to a region outside the outer-edge portion of the document. With respect to this shadow region, similarly to the technology disclosed in Japanese Unexamined Patent Application Publication No. 9-284497, if the scanning data is converted into the binary data using a prepared gray scale transform table, there is a high probability that a problem similar to the above-described problem will occur.